Filter



Nov. 20, 1951 c. G. VOKES 2,575,900

FILTER Filed Aug. 15,1946 2 SHEETS-SHEET l EUE/Z'ZZ CeccZ G. VOA e6 Patented Nov. 20, 1951 FILTER Cecil Gordon Vokes, Guildford, England, assignor to Vokes, Limited, Guildford, England, a British comp any Application August 13, 1946, Serial No. 690,096

In Great Britain March 16, 1945 4 Claims. 1 This invention relates to filters having automatic by-pass arrangements and more particularly to an outside-to-in filter having the by-pass efiiciency of an inside-to-out.

A filter construction in extensive use comprises a casing having a header containing the inlet and outlet openings with one of said openings centrally disposed, and a filter cage having a centrally disposed opening in its top, the cage being spring retained against the header with the centrally disposed openings in communication.

This construction may be used as an inside-tout filter wherein its central openings comprise the inlet and the filter cage may be efiiciently displaced by internal pressure to provide a bypass directly between the inlet and outlet.

In this instance the interior of the filter cage is relatively difiicult to clean. On the other hand, the construction may be employed as an outsideto-in filter wherein the central opening comprises the outlet and the collected dirt is easily cleaned from the casing and the outside of the filter element. In this instance, the filter cage is not susceptible to inlet pressure for by-passing movement.

The present invention provides an arrangement generally very similar but with the interior of the unit on the clean side and so arranged as to open a substantially annular by-pass valve giving substantially direct access of surrounding practical purposes be short-circuited.

In the preferred forms, the filter has an enclosing casing formed by a cylindrical body and a header and a filtering unit in the casing, the header having means affording entry of unfiltered fluid to the casing surrounding a central outlet for filtered fluid from the unit, a substantially annular by-pass valve, being spring controlled to open under pre-determined back pressure and lying in substantially the direct path across the top of the unit between the incoming fluid and the central outlet, so that the casing will for practical purposes be short-circuited.

In one form, the arrangement is such as to cause the unit to move bodily away from the outlet, a joint between the unit and the outlet serving as the by-pass valve. In such a form, the preferred method of ensuring that excess back pressure, when the direction of flow is from outside to inside the unit, will move the unit away from the outlet, is suitable to shield an appropriate area of the outer surface of the unit from the external pressure and preferably to subject it to the internal pressure. A flexible shield enclosing a space between an area of the unit and the outer casing or some other suitable abutment surface on the side remote from the outlet will serve to ensure that there is a sufiicient resultant pressure tending to move the unit away from the outlet against a retaining spring for such movement to take place when a predetermined back pressure occurs and at the same time the flexibility permits such movement. A flexible fabric sleeve surrounding a compression spring between the bottom of the unit and the bottom of the casing is a preferred form: or the flexible shield could be resilient and might serve also as the spring, for instance a copper bellows surrounding or surrounded by or replacing the compression spring. The shield might itself serve as part of the filter screen, taking for instance the form of a corrugated sleeve of felt or the like similar to that used as the filter screen of the unit.

In another form, a substantially annular bypass valve is normally held to a seating inside the unit by a control spring inside the unit and opens a corresponding series of apertures in the wall of the unit lying in substantially the direct path between inlet and outlet.

Typical examples of both forms are shown by the accompanying drawings in which:

Fig. l is a central section of a form in which the unit moves bodily, and

Fig. 2 is a similar view of a form in which an annular valve controls an annular series of apertures in the upper end cap of the unit.

In each case, the enclosing casing is formed by a cylindrical body I suitably secured to a header 2. The header is formed with a central outlet spigot 3 communicating with a socket 4 for receiving the outlet pipe. The inlet of the unfiltered fluid is from the space 5 surrounding the inlet 3 and communicating with the socket 6 for receiving the inlet pipe. In each case also, the filtering cage is shown as a star-shaped or deeply pleated filtering screen 1 surrounding a perforated metal supporting cylinder 8 and held between upper and lower end caps 9 and Ill which form the top and bottom walls of the filter cage.

Referring now specifically to Fig. l, a flexible fabric sleeve H is shown, surrounding a compression spring l2 between the bottom end cap it of the unit and the bottom of the casing l. The shield H is permanently attached to the unit. As shown, the typical cage with a filtering assembled by a central rod 22 and nut 23. upper end cap 9 hasa neck 24 extending into 25 carrying jointing material 25.

3 wall I of the star-shaped or deeply pleated type has a central tube l3 so that it can slide on a central bolt 14 holding the outer casing l to the header 2. The upper end plate 9 of the cage is secured to the top of the tube I3 and has apertures [5 to deliver the fluid to the outlet 3. At the lower end of the tube I3 is a flanged fitting IE to which the lower end plate I0 is held by a locking'nut I1, the lower end plate l0 having apertures I 8 into the space beneath. Attached to the rim of the lower end plate by a retaining band 20 is the corrugated felt sleeve II enclosing the compression spring l2 so as to make joint with the casing l at the bottom. When the easing is removed from the header (possibly by unscrewing an internally threaded captive portion I 9 of the assembly 'bolt [4 from outside the header) the cage can be withdrawn complete with sleeve and spring and dismantled by unscrewing the locking nut ll. Dirt or sludge remain in the bottom of the outer casing and can :be discharged when it is removed, or a drain plug may be provided as at 2!.

In operation the outsidepressure acts upon the portion of the upper end cap 9 outsidethe outlet 3. The lower end cap I0 is subject to the inside pressure on both sides. When the outside pressure is sufliciently in excess of the inside pressure, the unit will move down against the spring pressure and flow will take place between header inlet 5 and outlet 3, short-circuit ing the casing.

Referring now specifically to Fig. 2, the cage is The assembly or removal of the cage, which it holds with the joint 25 firmly seated on the outlet spigot 3.

In operation, when the determined back pressure is reached, the external pressure acting on the Valve 28 is sufficiently greater than the pressure inside the cage to move the valve from its seating and by-pass takes place direct from the inlet 5 through the annular series of apertures 32 and up the neck24 into the outlet 3, thus for practical purposes by-passing the casing I. A drain plug 2| may be provided.

I claim:

1. A filter unit, comprising a casing having an inlet and an adjacent outlet both in the top wall thereof, a filter cage having top and bottom end walls and an outlet in the top end wall thereof, said cagebeing mounted in said casing with its outlet aligned with said casing outlet and its top wall extending laterally beyond said casing outlet and subject to inlet pressure, means in said casing for resiliently biasing said cage against thetop wall of said casing for direct communication between said cage and easing outlets, and .a shield extending between the bottom endwall of said cage and said casing and shielding the bottom of said cage from inlet pressure, whereby said cage may be bodily moved by excessive inlet pressure to bypass across the top of said cage directly between said inlet and easing outlet.

2. A filter unit as defined in claim 1, wherein said shield comprises a compressible sleeve ex tending between the bottom end wall of said filter cage and the bottom wall of'said casing.

3. A filter unit as defined in claim 2, wherein said sleeve comprises flexible. material and is secured at one end to the bottom end wall of said filtercage and at the other end to the bottom wall of the casing. I

4. A filter unit as defined in claim 1, wherein the means for biasing said cage comprises a coil spring between the bottom .of said cage and the casing, and the shield comprises a flexible sleeve surrounding said spring and secured at its upper end to the cage and pressed at its lower en against said casing by said spring.

CECIL GORDON VOKES.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

